The spill occurred yesterday, on April 19, following a road traffic collision. But a cleanup operation is still underway for the second day today, on April 20, causing continued delays for drivers.
Oil was spilt after a lorry collided with the central reservation.
National Highways reported this morning the cleanup was still taking place and would likely last through the morning.
It said: “The M25 clockwise in Hertfordshire remains closed between J23 and J25.
“The road is likely to remain closed throughout the morning due to the complex nature of the clean-up.
“There are delays of 90 minutes between J21 and J23.”
The agency asked drivers to consider alternative routes to lessen delays.
More to follow.